﻿<p><em>IfcRelAssociatesMaterial</em> is an objectified relationship between a
material definition and elements or element types to which this
material definition applies.</p>

<p>The material definition can be:</p>
<ul>
<li>assigned to an element occurrence as a specific usage of a
layer set or profile set</li>
<li>assigned to an element occurrence or element type as a layer
set, profile set, constituent set or a single material</li>
</ul>
<p>Materials can be arranged by layers and applied to layered
elements. Typical elements are walls and slabs.</p>
<ul>
<li>An <em>IfcMaterialLayerSet</em>, for layered elements with an
indication of the layering direction and individual layer
thicknesses</li>
<li>An <em>IfcMaterialLayerSetUsage</em>, i.e. a material layer set
with positioning information along the reference axis or surface
of the element.

<blockquote class="note">
NOTE&nbsp; As a material layer set usage is an
occurrence based information, that applies to each individual
element, it cannot be assigned to an element
type.
</blockquote>

</li>
</ul>
<p>Material can be applied to profiles. Typical elements using
profile material are beam, column, member</p>
<ul>
<li>An <em>IfcMaterialProfileSet</em>, i.e. a set of material
assigned to a set of profiles, with a single material assigned to
a single profile as the default.</li>
<li>An <em>IfcMaterialProfileSetUsage</em>, i.e. a material profile
set with positioning information relative to the element axis,
also refered to as cardinal point.
<blockquote class="note">
NOTE&nbsp; As a material profile set usage is an
occurrence based information, that applies to each individual
element, it cannot be assigned to an element
type.
</blockquote>

</li>
</ul>
<p>Materials can be arranged by identified parts of a component
based element. Typical elements are dorrs/windows (with
components such as lining, framing and glazing), or distribution
elements.</p>
<ul>
<li>An <em>IfcMaterialConstituentSet</em>, for component based
elements with an indication of the component by keyword to which
the material consituent applies.
<blockquote class="note">
NOTE&nbsp; See the material use definitions at each
applicable subtype of <em>IfcElement</em> or <em>IfcElementType</em>
for a provision of these keywords.
</blockquote>
</li>
</ul>

<p>As a fallback, or in cases where only a single material
information is needed, material information can be directly
associated</p>
<ul>
<li>A single <em>IfcMaterial</em> for any element where the
material use definition does not prohibits its direct
association</li>
<li>An <em>IfcMaterialList</em>, e.g. for composite elements,
without an information, how the different materials are arranged.

<blockquote class="deprecated">
DEPRECATED&nbsp; The use of <em>IfcMaterialList</em> is deprecated in IFC4 onwards. Use
<em>IfcMaterialConstituentSet</em> instead.
</blockquote>

</li>
</ul>
<p>The <em>IfcRelAssociatesMaterial</em> relationship is a special
type of the <em>IfcRelAssociates</em> relationship. It can be
applied to subtypes of <em>IfcElement</em> and subtypes of
<em>IfcElementType</em>.</p>
<ul>
<li>The <em>IfcElement</em> has an inverse relation to its material
definition by the <em>HasAssociations</em> attribute, inherited
from <em>IfcObject</em>.</li>
<li>The <em>IfcElementType</em> has an inverse relation to its
material definition by the <em>HasAssociations</em> attribute,
inherited from <em>IfcPropertyDefinition</em>.</li>
</ul>
<p>If both, the element occurrence (by an instance of
<em>IfcElement</em>) and the element type (by an instance of
<em>IfcElementType</em>, connected through
<em>IfcRelDefinesByType</em>) have an associated material, then the
material associated to the element occurrence overrides the
material associated to the element type.</p>
<blockquote class="history">HISTORY&nbsp; New entity in IFC2x.</blockquote>
<p class="spec-head">Informal Propositions:</p>
<ol>
<li>An <em>IfcMaterialLayerSetUsage</em> shall not be associated
with a subtype of <em>IfcElementType</em>, it should only be
associated with individual occurrences</li>
<li>An <em>IfcMaterialProfileSetUsage</em> shall not be associated
with a subtype of <em>IfcElementType</em>, it should only be
associated with individual occurrences</li>
</ol>